Lipase L1 from Geobacillus stearothermophilus L1 contains an unusual extra domain, making a tight intramolecular interaction with the main catalytic domain through a Zn 2+ -binding coordination. To elucidate the role of the Zn 2+ , we disrupted the Zn 2+ -binding site by mutating the zinc-ligand residues (H87A, D61A/H87A, and D61A/H81A/H87A/D238A). The activity vs. temperature profiles of the mutant enzymes showed that the disruption of the Zn 2+ -binding site resulted in a notable decrease in the optimal temperature for maximal activity from 60 to 45-50°C. The mutations also abolished the Zn 2+ -induced thermal stabilization. The wild-type enzyme revealed a 34.6-fold increase in stabilization with the addition of Zn 2+ at 60°C, whereas the mutant enzymes exhibited no response to Zn 2+ . Additional circular dichroism spectroscopy studies also confirmed the structural stabilizing role of Zn 2+ on lipase L1 at elevated temperatures.

We synthesized new nonlinear optical (NLO) chromophores containing a 3,5‐bis(3,5‐bisbenzyloxy‐benzyloxy)‐benzoate dendron. Tricyanopyrroline (TCP)‐based chromophores were designed and prepared by virtue of its strong electron withdrawing property. A soluble polyimide containing 6‐({4‐[2‐(1‐allyl‐4‐cyano‐5‐dicyanomethylene‐2‐oxo‐2,5‐dihydro‐1H‐pyrrol‐3‐yl)‐vinyl]‐phenyl}‐butyl‐amino)‐hexanoyl group in the side chain was also prepared as an NLO active host polymer. A benzoate dendron was tethered at two different binding positions of the chromophore to yield two different guest molecules. Thin‐film composites of these dendronized chromophores dissolved in the NLO active polyimide host were employed to fabricate the electro‐optic (EO) samples. The EO properties of new NLO polyimides containing dendronized chromophores were compared with those of the sample with nondendronized plain chromophores. The effect of a bulky dendron on the EO properties was investigated using an in situ reflection technique. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5064–5076, 2008

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A new soluble and thermally stable nonlinear optical (NLO) polyimide was synthesized by adding both tricyanopyrroline (TCP)-and tricyanofuran (TCF)-based NLO chromophores into the polymer backbone. The NLO polyimide (PI-II) bearing two different chromophores with different sizes has a glass transition temperature of 146 o C and exhibits good film forming properties. The electro-optic coefficient of the film was 84 pm/V at 1.3 µm under a poling field of 80V/µm, even though PI-II has an unusually high chromophore density of approximately 20 wt% of TCP chromophores and 23 wt% of TCF chromophores. Even with a overall chromophore loading of 43 wt%, no severe aggregation effect was observed for the sample that exhibited a relatively high EO coefficient.